Do bugs feel pain?

Six-Legged Soldiers: Using Insects as Weapons of War

Entomologists estimate there to be around a quintillion individual insects on the planet–and that’s just insects. Bugs are everywhere, but how much do we really know about them? Jeff Lockwood to the rescue! Professor Lockwood is answering all your bug questions–one at a time, that is. Send your question to him care of blog@oup.com and he’ll do his best to find you the answer.

Do bugs feel pain? Like, how does the exoskeleton work?

Well, it’s hard to know. But then it’s hard to know what any organism experiences. For that matter, I’m not even sure that you feel pain—or at least that your internal, mental states are the same as mine. This is the “other minds” problem in philosophy. At least other people can tell us what they feel (even if we can’t be certain that their experience is the same as ours), but we can’t even ask insects. However, we can have three rather compelling lines of evidence that our six-legged brethren feel pain.

First, insects have a nervous system that resembles ours in many ways. That is, they see, hear, smell, taste, and feel. Many of our pains arise from pressure, shock, heat and other stimuli administered at high levels—and insects most assuredly respond to these bodily sensations.

Insects can even detect stimuli that are outside of our sensory scope. For example, butterflies can see ultraviolet wavelengths and bees can detect the plane of polarization of light.

Next, there are relevant biochemical similarities between insect and human nervous systems. At least some invertebrates possess endorphins and enkephalins. These chemicals are opioids (think opium) produced by the body to alleviate pain and stress. So the presence of these in insects suggests that they might experience pleasure/pain. We also know that the mechanisms of neural transmission are similar in insects and humans. This is one of the reasons that neurotoxic insecticides also poison you along with the cockroach in your kitchen. In fact, the organophosphate insecticides are based on the nerve gases developed during World War II. Kinda creepy, eh?

Finally, from an evolutionary perspective the awareness of pain is an enormously adaptive mechanism. Feeling pain when you touch something hot allows a fast response—and a learning opportunity. So it is unreasonable to assume that pain is unique to humans. In fact, this perception might reasonably be expected in organisms whose survival can be augmented by the experience of pain, either as part of an escape mechanism or as a basis for the capacity to learn from past experience. Insects have lots of things inflicting damage on them (fly swatters, bug zappers, lizards, bats, entomologists, etc.) and they certainly have the ability to learn (one experiment showed that headless cockroaches can learn—which is possible because insects don’t stuff all of their neural processing into their heads, like we do). So it seems quite reasonable that insects would have evolved the capacity to feel pain.

About 30 years ago, an eminent insect physiologist addressed the question of pain in insects. Vincent Wigglesworth (seriously, that was his name) argued that insects experience internal, visceral pain as well as pain caused by heat and electrical shock. However, he inferred from observations that cuticular damage did not cause pain. For example, an insect doesn’t limp when its leg is damaged. And this leads to your question about the exoskeleton.

The insect’s exoskeleton is, well, a skeleton. It works like a knight’s armor to provide protection. The exoskeleton also provides support and a solid shell for the attachment of muscles. And in a sense, it also serves as the insect’s skin (imagine your skin being tanned leather). The difference is, however, that piercing the exoskeleton doesn’t produce the same sorts of pain responses that cutting into our skin would evoke.

So, given that we can’t be sure whether insects experience pain, how should we treat these creatures? When I was teaching insect anatomy and physiology I insisted that the students anesthetized insects before conducting experiments that we would expect to inflict pain on a mouse. My rationale is two-fold.

First, it seems ethically obligatory to guard against the possibility that insects feel pain. If we use anesthetic and it turns out that insects don’t experience pain, the material cost of our mistake is very low (a few extra minutes to apply cold or carbon dioxide). However, if we don’t use anesthetic and it turns out that the insects were in agony, then the moral cost of our mistake is quite high.

Second, I think that treating insects as if they can experience pain cultivates an attitude of respect toward living organisms. And this seems like a good thing. We learn the methods of dissection through practices—and we also learn virtues such as compassion through practice. Perhaps we become overly careful in our actions by including animals that aren’t sentient, but a world that is more mindful of other beings than is strictly necessary is okay with me.

Of course, there are circumstances in which we are justified in crushing, poisoning, or otherwise harming insects. Nobody wants to suffer hunger or malaria. We must protect our food and bodies. And so inflicting suffering and death is part of life; we live with the existential dilemma that we must kill to live. But we are also obligated to minimize the harm that we do—and insects are a part of this duty.

Jeffrey Lockwood was hired as an insect ecologist at the University of Wyoming in 1986. But over the course of 20 years he metamorphosed into a Professor of Natural Sciences & Humanities, with a joint appointment between the Department of Philosophy and in the MFA program in Creative Writing. He teaches courses in natural resource ethics, environmental justice and the philosophy of ecology, along with creative non-fiction writing workshops. He is the author of Six-Legged Soldiers: Using Insects as Weapons of War.